Watch: Haj pilgrims pray on Mount Arafat

More than 1.5 million Muslims will pray on Mount Arafat in soaring temperatures on Saturday, in the high-point and most gruelling day of the annual Haj pilgrimage.

Worshippers from all over the world will climb the rocky, 70-metre (230-feet) hill, about 20 kilometres (12 miles) from Makkah, where the Prophet Mohammed is believed to have given his last sermon.

The desert summer heat is expected to hit 43ºC (109.4 degrees Fahrenheit), creating challenges especially among the elderly during a day of prayer and reciting the holy Quran.

Stay up to date with the latest news. Follow KT on WhatsApp Channels.

The Haj, which takes at least five days to complete and is mostly outdoors, "is not easy because it is very hot", said Abraman Hawa, 26, from Ghana.

"We have sun... but it is not as hot. But I will pray to Allah at Arafat, because I need his support," she added.

Saudi authorities have urged pilgrims to drink plenty of water and protect themselves from the sun. Since men are prohibited from wearing hats, many carry umbrellas.

More than 10,000 heat-related illnesses were recorded last year, 10 percent of them heat stroke, a Saudi official told AFP this week.

The Haj, one of the world's biggest religious gatherings, is increasingly affected by climate change, according to a Saudi study that said regional temperatures were rising 0.4ºC each decade.

But Mohammed Farouk, a 60-year-old Pakistani pilgrim, was not put off by the Gulf kingdom's scorching summer sun.

The Haj is "very important for me as a Muslim", he said.

The enormous crowds of worshippers spent the night in a giant tented city in Mina, a valley several kilometres outside Makkah, Islam's holiest city.

Many of them were tightly packed in the air-conditioned tents, lying close together on narrow mattresses.

They were grouped by nationality and price, depending on how much they had paid for their Haj packages -- usually several thousand dollars.

• The Haj, one of the five pillars of Islam